Why hurricane season is about to pick up

Jun 30, 2023

Meteorologist Sean Sublette examines the warm Atlantic water and explains why the hurricane season may be ready to jump.

A few weeks before the Atlantic hurricane season started June 1, conventional wisdom was for a season that was near average. In this case, an average season has 14 storms strong enough to take on names. Of those, seven become hurricanes, with three of those becoming major hurricanes.

Often misused, the term major hurricane is defined as one that reaches Category 3 on a scale from 1 to 5 — meaning its strongest sustained winds are at least 111 mph. This is the point at which an ordinarily well-framed house can lose the wooden boards that make up its roof. Plus, the power outages in the wake of a storm that strong can last for several days, if not weeks.

The remains of homes demolished after heavy damage from Hurricane Ian are seen in the Tropicana Sands mobile home park May 10 in Fort Myers, Fla.

Two competing physical processes are in conflict for the rest of this season.

The first is the El Niño phenomenon. A periodic warming of the central and eastern Pacific Ocean near the equator, it is also linked to an increase in winds from west to east across the tropics. However, tropical systems tend to move from east to west, so these competing wind directions make it more difficult for storms to organize and form. In effect, this wind shear keeps the energy — oceanic thunderstorms — from concentrating into a circulation that creates a tropical storm.

And after three years on hiatus, El Niño has come roaring back in the last three months.

Current surface water temperature across the North Atlantic Ocean (21 July 2023)

The second is the current Atlantic Ocean temperatures, which have gotten a lot of attention recently as they are so much warmer than normal. Warm ocean water is the fuel for tropical systems, so the warmer the water, the more potent the fuel for storms.

The story of the irresistible force meeting the immovable object comes to mind, with the Atlantic water temperatures as the force and El Niño as the object.

But the analogy is not that simple. El Niño will not prevent the storms from forming, it just tends to make the environment more difficult for them to form. Hurricane Andrew is the prototypical example. Striking South Florida in 1992, it was the first storm of that season, not forming until the third week of August toward the end of an El Niño. At the time, it became the costliest hurricane on record in the United States, and it remains in the top 10 today, even adjusting for inflation.

With a huge area of the tropical Atlantic now 3-5°F warmer than normal, most professional institutions have revised their projections for the season. Among those is the well respected Colorado State University Tropical Meteorology Project. In their July 6 update:

“... sea surface temperatures in the eastern and central tropical Atlantic are now at record levels, so despite the high potential for an El Niño, the impacts on tropical Atlantic/Caribbean vertical wind shear may not be as strong as is typically experienced given the extremely warm Atlantic.”

In the observational records, we have not seen a rapidly developing El Niño of this magnitude while Atlantic Ocean temperatures are so high. It may be better to think of the rest of the season like a series of cars that have trouble starting, but any one that does manage to start will accelerate dramatically.

In other words, there still may be a normal number of storms this year, but the ones that do form will tend to be stronger. Not surprisingly, this is the current understanding of how the tropical Atlantic is expected to behave as the climate warms.

More concerning, the warming climate also comes with higher sea levels, so the coastal flooding from storm surge is deeper and progresses farther inland from a storm’s landfall point. Warmer water means more evaporation from the oceans into the storms, which leads to heavier rain — even as the storm slowly decays hundreds of miles inland, increasing the flood risk of streams and rivers far away from the coast.

The Atlantic hurricane season peaks from mid-August to mid-October

It has been quiet in July, which is absolutely normal. The peak of the hurricane season is from mid-August to mid-October, so we are about to find out how hard it will be to start these heat engines and see how fast they will go.

Basic Disaster Supplies Kit

To assemble your kit store items in airtight plastic bags and put your entire disaster supplies kit in one or two easy-to-carry containers such as plastic bins or a duffel bag.

A basic emergency supply kit could include the following recommended items:

• Water (one gallon per person per day for several days, for drinking and sanitation)

• Food (at least a several-day supply of non-perishable food)

• Battery-powered or hand crank radio and a NOAA Weather Radio with tone alert

• Flashlight

• First aid kit

• Extra batteries

• Whistle (to signal for help)

• Dust mask (to help filter contaminated air)

• Plastic sheeting and duct tape (to shelter in place)

• Moist towelettes, garbage bags and plastic ties (for personal sanitation)

• Wrench or pliers (to turn off utilities)

• Manual can opener (for food)

• Local maps

• Cell phone with chargers and a backup battery

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Meteorologist Sean Sublette examines the warm Atlantic water and explains why the hurricane season may be ready to jump.